1. Field of the Invention
The present invention relates to a magnetic tape cassette. It particularly relates to an original compact magnetic tape cassette whose size is not larger than that of the magnetic tape cassette of the Philips type and which is used for audio equipment or the like.
2. Background of the Invention
Since the size and weight of a cassette tape recorder has recently been reduced, the use of a compact magnetic tape cassette recorder for this reduced-sized cassette tape is spreading. At the same time, it is being strongly desired that a magnetic tape cassette appropriate for long-length recording and reproduction of high quality and density be available in the field of audio technology. There is known a magnetic tape cassette so as to achieve the above desire. This tape cassette uses digital recording and reproduction, which are performed through the pulse conversion of an input signal by pulse code modulation in contrast with analog recording and reproduction.
A large video tape cassette for digital recording and reproduction has generally become popular. In this large tape cassette, the frequency band is made wider than that for a conventional compact audio tape cassette because the frequency band needs to be made about five times as great as that for the conventional compact audio tape cassette. Except in some special cases, the large video tape cassette is matched with a rotary head system. The large video tape cassette has such a construction that a guard panel openable from the cassette is provided on the cassette to close its front opening because sufficient tape protection measures for higher reliability become necessary to perform high-density and wide-frequency-band digital recording and reproduction in which the wavelength of a recorded signal is shorter than that for the conventional compact audio tape cassette.
A very compact magnetic tape cassette, which meets the above mentioned desire, is suitable for audio recording and reproduction or the like. The frequency band for this very compact cassette is relatively wide as well as that for the large video tape cassette. Since the very compact magnetic tape cassette is not larger than the conventional compact audio tape cassette, the very compact magnetic tape cassette is expected to be carried outdoors at least as often as the conventional compact audio tape cassette. For that reason, the very compact magnetic tape cassette needs to have such a construction as to surely prevent the jamming of a magnetic tape due to its looseness which would be caused by its carrying or the like.
In such a very compact magnetic tape cassette proposed to have the above-described construction, a locking member is provided so that hubs on which a magnetic tape is wound are locked out of use and are unlocked during use. The locking member is always urged toward the hubs by a spring. When the magnetic tape is out of use, sharp-pointed projections provided on the locking member are located in contact with the hubs to keep the hubs from rotating. When the magnetic tape is in use, the sharp-pointed projections are separated from the hubs. However, as the component parts of the cassette are made smaller to render it compact, it becomes less easy to assemble the component parts. Since the locking member is urged by the spring when the locking member is attached in the assembly, it is troublesome to handle the locking member and the efficiency of the assembly is therefore degraded. Furthermore, the locking member is always urged toward the hubs (rearward of to the cassette) by the spring to lock the hubs. But, when the locking member is slid forward of the cassette through engagement with the guard panel at the time of opening of guard panel to unlock the hubs, the locking member is elastically deformed to make it unsure that the locking member is engaged with the guard panel. These are problems.